JPS62234510A - Drying method for regenerated hollow cellulose yarn - Google Patents

Abstract

PURPOSE:To dry regenerated porous hollow cellulose yarn while maintaining the performance thereof by bundling said yarn and replacing the moisture in the hollow yarn with an org. solvent having <=70 deg.Cb.p., and >=10wt% solubility in water and having no hydroxyl groups, then stretching and elongating the hollow yarn. CONSTITUTION:Many pieces of the porous hollow cellulose yarn which is prepd. from a cellulose-cuproammonium soln. and is in a wet state are bundled to form a honeycomb structural body. The moisture in the hollow yarn is replaced with the org. solvent having <=70 deg.Cb.p., and >=10wt% solubility in water and having no hydroxyl groups. An acetone is representatively used as said org. solvent. The yarn is subjected to stretching then to drying after the replacement. The hollow yarn which is poorer in the form retentivity in the wet state is more preferably subjected to the multi-stages replacement at the time of replacing the moisture with the acetone. The regenerated porous hollow cellulose yarn which is inferior in the form retentivity in the wet state is thereby efficiently dried in a large amt. while approximately the same performance as the performance in the wet state is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for drying porous regenerated cellulose hollow fibers in a wet state. More details.

When drying porous regenerated cellulose hollow fibers obtained from a cellulose steel ammonia solution, the hollow fibers are bundled to form a honeycomb structure, water etc. in the hollow fibers are replaced with an organic solvent, and the honeycomb structure is further removed. This invention relates to a drying method for stretching and drying a body.

In addition, "porous hollow fiber" in the present invention refers to a thickness of 0.02μ on the surface of the wall thickness when the wall thickness is observed with an electron microscope.
It is defined as a hollow fiber in which pores of m or more are observed at 106 pieces/cut or more, and those that are not observed are defined as "non-porous hollow fiber".

The porous regenerated cellulose hollow fibers obtained in the present invention are useful for separating and concentrating target components in liquid or gas mixtures containing water. It can also be used as a separation membrane to separate and remove bacteria, including fils, rickettsia, chlamydia, mycoplasma, etc., dispersed in an aqueous solution that dissolves tannolytes and electrolytes, or to separate and concentrate tannolytes from an aqueous solution containing microbial particles. I can do it.

<Conventional technology> Among the separation and purification technologies for substances, research is being actively conducted on membrane separation technology as a means of separating micron-order substances such as ions, low-molecular substances, and suspended solids and fine particles in the liquid phase. ing. The biggest problem preventing commercialization of this type of technology on an economic scale is that the rate of material separation is low.

Since the substance separation rate depends on the membrane area, the membrane area must be increased as the amount of substance to be treated increases.

The normally used flat membrane inevitably increases the size of the device.

This problem can be solved by separating substances using extremely thin hollow fibers and using the fiber wall surrounding the hollow part as a separation membrane, and by bundling a large number of these hollow fibers to form a substance separation part. This can be solved by increasing the effective area of the device and downsizing the device. Fields in which membrane separation systems may become the main focus in the future include: ■ Fields that require concentration and purification at low temperatures and 1-rot yield (food, biochemical industry fields), ■ Fields that require sterility and dust-free operation (pharmaceuticals, etc.) and treatment institutions, electronic industry field), ■Concentration and recovery of trace amounts of expensive substances (nuclear power 1
Hydrophilic membranes with large pores that are easy to handle are the membranes used in these fields. There is a growing need for

Regenerated cellulose is a highly hydrophilic material. Regenerated cellulose has excellent organic solvent resistance and mechanical properties,
Also, unlike synthetic polymers, it is less toxic to living organisms. Therefore, the appearance of hollow fibers composed of regenerated cellulose and having a large average pore diameter was expected.

The present inventors first discharged the cellulose steel ammonia solution through the annular spinning spout, solidified it, regenerated it, and washed it with water. The coagulable liquid is discharged from the central spinning port,
Furthermore, by causing microphase separation before coagulation, we succeeded in fabricating a porous regenerated cellulose hollow fiber T-fiber structure having a continuous hollow portion extending throughout the entire fiber length.

<Problems to be solved by the invention> However, since porous regenerated cellulose hollow fibers have pores with an average pore diameter of 0.02 to 10 μm in the wall thickness (inner and outer walls), conventional non-porous regenerated cellulose A method for drying cellulose, for example, a method in which hollow fibers in a wet state are fed into a high-temperature dryer, and the moisture in the hollow fibers is heated and evaporated by passing the hollow fibers continuously through this porous regenerated cellulose hollow fiber. If applied as is, problems such as collapse of the hollow portion of the hollow fiber and collapse of holes in the thick wall portion will occur. As a result of intensive research to overcome the above problems, the present invention has been achieved.

The purpose of the present invention is to solve the problems of the prior art as described above (such as the collapse of the hollow part of the hollow fiber and the collapse of the pores in the thick wall part), and to improve the function of the porous regenerated cellulose hollow fiber in a wet state. It is an object of the present invention to provide a method for efficiently drying without causing any damage.

Means for Solving Problems> The method for drying porous regenerated cellulose hollow fibers according to the present invention includes the steps of drying the hollow fibers in a wet state in the production 11 of porous regenerated cellulose hollow fibers. The hollow fibers are bundled to form a honeycomb structure, and the water etc. in the hollow fibers are replaced with an organic solvent having a boiling point of 70°C or less, a solubility in water of 10vt% or more, and no hydroxyl group, and further It is characterized by stretching and drying the honeycomb structure.

In the present invention, "wet state" means that the surface tension is 40 dyn/
It means a state in which 10 wt % or more of a so-called highly polar solvent having a boiling point of 80° C. or higher is contained, and a typical example thereof is a state in which water is contained.

Porous regenerated cellulose hollow fibers in a wet state made from a cellulose steel ammonia solution have excellent hydrophilicity and are porous, so their shape retention is slightly inferior to that of non-porous hollow fibers. Therefore, when removing solvents from a state containing solvents with high surface tension such as water, the cross-sectional shape of the hollow fibers often changes and the porosity disappears.

- It is preferable that the porous regenerated cellulose hollow fibers according to the strength tree invention have a circular cross section or an elliptical cross section close to the circular cross section, and for this purpose, a large number of the hollow fibers are bundled to form a honeycomb structure. As a strong hollow fiber bundle,
Drying is the most important feature of the method of the present invention. Here, "honeycomb structure" means that when the cross-sectional shape of the hollow fibers is approximated to a circular cross-section, by bundling a large number of hollow fibers with the same cross-section, when viewed from the cross-sectional direction of the hollow fibers,
It means a structure that has a nest-like structure ()/bicam structure). By forming and drying this honeycomb structure, deformation of the cross-sectional shape of the hollow fibers during drying can be prevented.

The method of replacing water with an organic solvent and drying is a common method, but as in the present invention, an organic solvent with a boiling point of 70°C or less, a solubility in water of 10 wt% or more, and no hydroxyl group is used. By replacing the moisture etc. in the hollow fibers, hollow fibers having almost the same performance as in a wet state can be obtained. When water is replaced with an organic solvent other than the organic solvent (for example, methanol or ethanol), the average pore diameter of the porous regenerated cellulose hollow fibers becomes significantly smaller during drying, sometimes 0.02 μm.
The following is true. It is common for hollow fibers to become hard and brittle after thorough drying. Therefore, it is essential to replace the moisture in the hollow fibers with an organic solvent that has a boiling point of 70°C or lower, a solubility in water of 10 wt% or higher, and does not have hydroxyl groups. Hollow fibers can be obtained that can fully exhibit their performance as hollow fibers used for. At the same time, hollow fibers with high flexibility can be obtained. Here, the term "hollow fiber" after drying refers to one with a moisture content of 10% or less. Acetone is preferably used as the organic solvent. In addition, when replacing water etc. with acetone, the poorer the shape retention in the wet state, the 50%, 70%, 90%, 10%
It is preferable to perform multi-stage replacement with 0%. If water is replaced with this acetone, the reason is currently unknown, but
Conventional non-porous hollow fibers are substituted with a solvent other than the organic solvent and dried, making them more flexible than hollow fibers, with lower crystallinity in terms of microstructure, and well-developed intermolecular and intramolecular hydrogen bonds. There are some characteristics such as not. (9) By stretching the honeycomb structure substituted with the organic solvent, the dimensional stability when wetted becomes very good. The optimal range of the draw ratio during stretching varies depending on the spinning conditions of the hollow fiber, but generally, if it is in the range of 5 coefficients or more and 15 coefficients or less, dimensional stability in wet conditions will be good. If it is 5% or less, it will elongate significantly when wet, and if it is 15% or more, it will shrink significantly.

As a drying condition, drying in a vacuum state is preferable because drying can be carried out in a short time, and the temperature does not need to be particularly limited, but it is preferably at least room temperature and at most the boiling point of the organic solvent.

Prior to the description of Examples, methods for measuring each characteristic value used in this specification will be shown below.

Calculate the average molecular weight (viscosity average molecular weight) Mv by substituting the intrinsic viscosity number [η]Cml/1/) measured in a copper ammonia solution (20 ° C.) into the following formula (1). do.

Mv=[η] X 3.2 X 103
(1) 0 average pore diameter, pore density If the number of pores existing in the pore radius r-dimension + dr of 1 cm2 porous membrane is expressed as N(r)dr (N(r) is the pore size distribution function), the average The pore radius et al and the pore density N are calculated by the following formula (2
) and (3). However, the average pore diameter is 2r5
So N = , 10-[r)dr (3
) Electron micrographs of the inner and outer wall surfaces and the intermediate surface of the thick wall portion of the porous regenerated cellulose hollow fiber obtained by the method of the present invention are taken using a scanning electron microscope. Sampling of the thick wall part was performed using a Waltra microtome (LKB (Sweden)) after embedding the hollow fiber in epoxy resin.
om* I 8800 model), samples with a thickness of 1 μm were sequentially cut from the outer wall surface to the inner wall surface. After de-embedding the sections with chloroform, electron micrographs are taken of each section. The pore size distribution function N (r) is calculated from the photograph by a known method and substituted into equation (2).

That is, the pore size distribution is determined, and a scanning electron micrograph of a small area is enlarged and printed to an appropriate size (for example, 20 scratches x 20 lines), and test lines (direct #s) are drawn at equal intervals on the resulting photograph.
Draw 20 lines. Each straight line crosses a number of holes. Measure the length of the straight line that exists within the hole when it crosses the hole, and find this frequency distribution function. Using this frequency distribution function, N(r) is determined, for example, by the method of StereoZo (for example, "Quantitative Morphology" by Norio Suwa, published by Iwanami Shoten).

0 Weight Shear Linkage The obtained porous regenerated cellulose hollow fibers are left at a temperature of 20° C. and a humidity of 65% for 16 hours or more.

After that, the hollow fiber was applied with a force y ) (Dr
The hollow fibers are then immersed in pure water at 25°C.

After 30 minutes, the length of the hollow fiber in a wet state is measured (We is the length). The Couette Sea linkage is given by equation (4).

Wet cable 1 linkage (I) = (We length - Dry length)/Dry length 0
(4) <Examples> The present invention will be specifically described below with reference to Examples.

Examples 1-5 Cellulose linter (viscosity average molecule i 2.3 X 1
05) prepared by a known method with an ammonia concentration of 6.8w
6.t% in a copper ammonia solution with a copper concentration of 3.1 wt%.
It was dissolved at 3 wt% and subjected to foaming to obtain a spinning stock solution.

The spinning stock solution was poured into the outer spinning spout (outer diameter: 2 mm) of the annular spinning spout for 2.9 m and 47 minutes, and the ratio of acetone and water was 6.
7.3wt%, the ratio of ammonia to water is 0.9
A mixed solution of wi% was spun at 2.5 d/min from the central spinneret (outer diameter 0.4 φ) so that the ratio of acetone and water was 67.
．． 3 wt%, and the ratio of ammonia to water is 0.9
Discharge directly into wt% mixed solution, 1Orrv5! j-
Make sure to wind it up at a speed of . Immediately after being discharged, the transparent blue fibrous material gradually turned white, coagulated while causing microphase separation, and maintained its shape as a fiber (hollow fiber). After that, it was regenerated with a 2wt sulfuric acid aqueous solution at 25°C,
Thereafter, it was washed with 25°C water. Hollow fiber 10 after washing with water
0 are bundled to form a honeycomb structure, 100wt%
It was immersed in acetone for 1 hour. Thereafter, this honeycomb structure was set in a tension stretching machine, stretched at different stretching ratios as shown in Table 1, and vacuum-dried for 2 hours. Table 1 shows the average pore size of the outer wall surface of the hollow fibers obtained.

[Table 1] The porous regenerated cellulose hollow fibers obtained in Examples 1 to 5 have good shape retention (deformation of hollow portions, etc.) and performance.

Further, as shown in Table 1, if the stretching ratio is within the range of 5 to 15%, the dimensional stability in the wet state is within about ±5% for 9-fold and Toshilin keso, which is very good.

Comparative Example 1 One wet hollow fiber obtained in Example 1 was replaced and stretched and dried in the same manner as in Example 3. As a result, the hollow part of the hollow fiber after Em was significantly deformed and the hollow part was blocked. There were also a mixture of places where this was done.

Comparative Example 2 100 wet hollow fibers obtained in Example 1 were bundled to form a honeycomb structure, which was immersed in 100 wt % methanol for 1 hour. After that, it was set in a tensile stretching machine, stretched by 10%, and vacuum dried for 2 hours. The shape retention of the obtained hollow fibers was very good, but the hollow fibers were nearly transparent, and as a result of observing the outer and inner wall surfaces of the hollow fibers with an electron microscope,
No holes could be observed. Therefore, the average pore size is 0.02
It is less than μm.

<Effects of the Invention> Since the present invention is configured as described above, by using the method according to the present invention, porous regenerated cellulose hollow fibers with poor shape retention can be brought into a wet state. However, the porous regenerated cellulose hollow fibers obtained by the method of the present invention can be used for drying without damaging the hollow fibers. For example, filtration/dialysis type or filtration type artificial kidney +11i, artificial liver, or hollow fiber for artificial pancreas can be used. This porous regenerated cellulose hollow fiber, which is hydrophilic and has excellent mechanical properties, is suitable for use in bio-related fields (medicine, biochemical industry) and food fermentation fields. .

It is also ideal for separating and concentrating or removing microorganisms such as fils from an aqueous solution containing tannophosphates.

Claims (1)

[Claims] 1. In the manufacturing process of porous regenerated cellulose hollow fibers obtained from a cellulose cupric ammonia solution, when drying the hollow fibers in a wet state, the hollow fibers are bundled to form a honeycomb structure. is formed, and the water, etc. in the hollow fibers is replaced with an organic solvent having a boiling point of 70° C. or less and a solubility in water of 10 wt% or more and having no hydroxyl groups, and then the honeycomb structure is stretched and dried. A method for drying regenerated cellulose hollow fibers. 2. The drying method according to claim 1, wherein the stretching ratio during stretching is 5% or more and 15% or less. 3. The drying method according to claim 1 or 2, wherein the organic solvent is acetone.